The episode unfolds in the vibrant yet eerie setting of 1994 Brooklyn, where a daring group of children venture into what seems to be an ancient, haunted sanitarium. Hardly have they stepped into one of its chambers when a thunderous crash echoes through the halls, revealing none other than Matty Brewer's older brother, Anthony 'Stink' Brewer (played by David Schwimmer), causing the commotion. As Matty hastily chases his brother away, the other children stumble upon an electrical junction box, still humming with eerie life. Intrigued, Matty is the sole soul to reach out and touch it, and in the blink of an eye, he appears to be succumbing to a strange, melting transformation.
Years leap forward to 2024, where twins Cece (Jayden Bartels) and Devin Brewer (Sam McCarthy) arrive in Brooklyn, eager to spend the summer with their father, Anthony. He welcomes them into his home, handing them informative packets designed to ensure their summer is both safe and enjoyable. Amidst his warnings to steer clear of the basement, Anthony offers them a glimpse of what resembles a botanical research lab, filled with intriguing gadgets and greens.
Their evening unfolds at a cozy dinner, where the family celebrates Cece and Devin's arrival while mapping out their summer adventures. Cece is thrilled about attending a debate camp in the city starting Monday, while Devin seems somewhat undecided about his plans. On their way out, Anthony and the twins bump into CJ (Elijah M. Cooper), prompting Anthony to suggest, albeit loosely, that Devin might spend his summer working at CJ and Gwen's restaurant. Devin, however, isn't overly enthusiastic about the idea.
Returning home, they find Jen (Isabella Ferreira) awaiting them in the driveway. Jen informs Anthony that Joe Jr. has filed a harassment complaint on behalf of Trey and returns Anthony's brother's belongings. When she attempts to broach the subject of the fateful night in 1994, Anthony hastily excuses himself to his lab, leaving Jen's words hanging in the air.
The next morning, Devin awakens to eavesdrop on Anthony's heated phone conversation with Tori, who is apparently hesitant about letting Cece attend the debate class. By the time Tori hangs up, Anthony catches Devin's curious eavesdropping. Cece briefly visits the kitchen but makes a swift exit, citing an urgent matter, leaving Anthony to enjoy his solo breakfast. Devin, curious, follows her trail.
At the pharmacy, Cece realizes that Devin's keen interest in hair styling products stems from his crush on Frankie (Galilea La Salvia) and their invite to the park from CJ. Admitting his attraction, the conversation stalls abruptly when a commotion at the entrance disrupts them – the manager attempting to usher away a troublesome customer. Seizing the moment, Cece diverts her attention to shoplifting beauty products, her eyes twinkling with mischief.
While Devin was at the park, he discovered that Frankie was in a relationship with Trey. To his surprise, the troublesome shopper from the pharmacy arrived, demanding payment from Cece's recent haul with an air of authority. Just as Devin and Cece prepared to depart, CJ showed up and led them to a gathering of other kids, where the conversation inevitably steered towards the mysterious disappearance of their uncle in 1994. It was evident that Cece and Devin were uneasy discussing the topic, yet Frankie was intrigued by Devin's apparent lack of fear. Trey, sensing an opportunity, attempted to embarrass Devin by daring him to visit the location where their uncle vanished.
Cece was even more distressed about Devin entering the room where their uncle's disappearance had occurred, pleading with him to reconsider. However, Devin was determined to impress Frankie and one-up Trey. Trey, growing increasingly frustrated as Devin remained in the room, seized the chance to act when no one was watching. He discovered a concealed electrical panel and, using his bolt cutters, deliberately shorted some contacts, plunging the area into darkness. Inside the room, the same eerie pattern from earlier replayed, and Devin began to undergo a transformation akin to his uncle's fate, slowly melting.Somehow, Devin managed to extricate himself and stumbled halfway down the tunnel, where Cece found him in a state of shock.
The following morning, Devin recalled only fragmented memories of entering the tunnel. As he and Cece argued over his reckless stunt, Anthony arrived and asked them to visit their grandmother, Naomi, at the nursing home, where she had reportedly had a tumultuous night. Cece conveniently used her debate camp commitments as an excuse, leaving Devin to face the task alone.
Upon their arrival, Naomi was ranting incoherently about finding Matty. Anthony, with some effort, managed to calm her down and introduced her to Devin. Soon after, Anthony was summoned by the doctor for a private conversation. Naomi, seizing the moment, clutched Devin and whispered that he smelled like Matty. When a nurse intervened, Devin eavesdropped on Anthony's discussion with the doctor about conducting tests. When they were alone, Devin inquired about Naomi's insistence on Matty being alive. Anthony explained that she had never accepted his death.
Hunger pangs struck both Devin and Anthony as they returned home from the nursing home. Anthony directed Devin to the takeout menus, encouraging him to indulge while he briefly descended to the basement. While scanning the menus, Devin stumbled upon an old photo album belonging to Matty. Meanwhile, Anthony found an oil/dirt stain on the Beasite Boys' t-shirt Matty wore on the day he disappeared. He scraped off a sample for closer examination under a microscope. While flipping through the album, Devin experienced a vivid flashback of Matty. He attempted to share it with Anthony, but the sample taken from Matty's shirt inexplicably came to life as a tiny plant. Before Anthony could react, the plant burgeoned into a colossal vine, dragging him around the basement. Simultaneously, Devin began hearing a loud, ominous humming, prompting him to flee outdoors and call Cece.
Outside, the vine erupted from the sewer and entangled Devin, choking him and nearly overpowering him. With a last-ditch effort, he grasped a steel pipe and struck a clamp securing a steel grate. The grate fell onto the vine, causing it to retract back into its original sample form. Devin awoke, clueless about how he had arrived at his current location, while Anthony discovered a rash spreading across his inner forearm.
